Many people spend a half an hour in the morning to dry their hair. This is non-productive time, which must be spent with a hairdryer in one hand. Thus there is need for a portable hair dryer that would dry the hair while the person is able to perform other morning duties. Several such devices have been patented already. The portable hairdryer of Waters (U.S. Pat. No. 3,946,498), which is a unit that hangs on the head, which is powered by a long extension cord. The cordless drier of Tomay (U.S. Pat. No. 5,195,253) teaches a handheld blower type dryer with both an electrical and thermal battery. This is also impractical since it requires the full time use of one hand.
The hands-free hair dryer of Sanders (U.S. Pat. No. 5,651,190) teaches a hair bonnet connected by a flexible hose to a battery pack worn on the back. This is not very practical for a number of reasons. The hose would interfere with many activities, and the heavy battery requires a strap to be attached to the body. And lastly the battery's longevity is very limited. Consider the worst-case example and assume that one needs to have the dryer at 1500 watts for 30 minutes. This equates to a total energy use of 2.7 mega joules. If this was powered by a 12 volt battery this would require a total charge of 225 coulombs. This is equivalent to 62.5 ampere hours, which is the capacity of a large conventional car battery.
Thus the battery-operated devices have not proven practical. Similarly the portable hair dryer of Stelly (U.S. Pat. No. 5,787,601) with a rechargeable battery pack has not proven practical.
The portable hair dryer of Bonnema (U.S. Pat. No. 5,857,262) is a gas-powered drier. While this will presumably store enough energy for a full cycle of drying as hydrocarbons are highly efficient energy storage units, this would still require the use of a hand to hold and control the dryer.
The hands-free dryer of Lee et. al. (U.S. Pat. No. 5,940,980) is essentially a conventional hand-held drier attached to a gooseneck tubing, which is attached to a large clip for attachment to convenient furniture or fixtures. This again is not very practical as it requires total focus on position of the head with respect to the dryer.
Finally the portable dryer of Porter (U.S. Pat. No. 6,058,944) teaches a bonnet and hose with a purse style hydrocarbon heater feeding the hot, dry air to the hose. This has some of the same limitations as some of the early devices in that it would require the carrying of the heater unit and the hose would be interfering with natural movements. In addition, the propane reservoir in the purse unit would have to be recharged on a regular basis.
Thus, in spite of the demonstrated need for a truly portable hair dryer no practical unit has been brought to the market.